Elevated antibody titers in Abdala vaccinees evaluated by Elecsys® anti-SARS-CoV-2 S highly correlate with UMELISA SARS-CoV-2 ANTI RBD, ACE-2 binding inhibition and viral neutralization assays

SARS-CoV-2, a recently emerged coronavirus, is causing high morbidity and mortality worldwide since December 2019, posing an enormous health, social and economic problem. Obtaining effective treatments that can diminish deaths and sequelae and vaccines to slow or prevent viral transmission, and reduce disease severity and/or death are of utmost importance. Abdala is a Cuban vaccine based on the recombinant RBD subunit of the spike protein expressed in Pichia pastoris yeast. It demonstrated high efficacy (92.28 %) in phase III clinical trials for reducing transmission, and more than 90% effectiveness in reducing disease severity and mortality. Antibody titers were evaluated in 42 Abdala vaccinees using the Elecsys® Anti-SARS-CoV-2 S test. Fifteen days after immunization, sera from vaccinees showed high antibody titers (median of 1595 U/mL). The results obtained in this study also demonstrate correlation between the Cuban test UMELISA SARS-CoV-2 ANTI RBD used during the clinical trials and Elecsys® test results.